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❒ Processing flow of MOCVD
Scientists called single crystal film as “Epitaxy,” which should be grown under very strict conditions. Currently, the most commonly used method to grow epitaxy in a production line is to use Metal Organic Chemical Vapor Deposition (MOCVD), and this technology requires High vacuum (UHV) and results in lower cost.  Making the example of growing GaAs epitaxy, the processing flow of MOCVD is shown in Fig. 1 and described as follows:
1. Placing GaAs wafer on top of wafer table of MOCVD machine as a substrate.
2. Under high vacuum, introducing different organic metallic gas AsH3 and Ga(CH3)3 into the reactor through the gas nozzle and moving toward the GaAs wafer (substrate).
3. Heating the substrate to a high temperature, so the chemical bond of AsH3 is broken to generate gallium atoms and the chemical bond of Ga is broken to generate arsenic atoms; and, generating GaAs molecules by chemical reaction.
4. Slowly accumulating GaAs molecules on the GaAs wafer (substrate) to form GaAs epitaxy. 

 
Figure 1: Illustration of MOCVD system.
 

❒ Features of MOCVD
MOCVD may also be called Metal Organic Vapor Phase Epitaxy (MOVPE). There is chemical reaction occurred in the process of film growth. MOCVD belongs to Chemical Vapor Deposition (CVD) and only requires High Vacuum (HV). The metal organic gas for reaction may be rapidly deposited on the substrate in a larger amount, so MOCVD may have lower cost and is suitable for mass production in factory. However, the flow volume of metal organic gas molecules injected from each pipe in the process of epitaxy growth is not easily controlled, i.e. the processing parameters are not easily controlled, MOCVD takes longer time to regulate suitable gas flow volume.
MOCVD is usually applied in a factory production line for LED, Laser diode (LD) or Radio Frequency Integrated Circuit (RFIC). It should be noted that most of the metal organic gas used for MOCVD is very toxic and a very small amount of gas leakage may cause explosion or death. Therefore, normally the factory will have very strict protection measures.
 
❒ Advantage and Disadvantage of MOCVD
➤ Advantage: MOCVD employs “High Vacuum” (HV) and has lower cost, so it is suitable for mass production in factory and is the most commonly used epitaxy growth technology in the production line nowadays.
➤ Disadvantage: The processing parameters are not easily controlled, so MOCVD is not suitable for research and development. The raw material is usually gas or liquid, so it is more difficult to regulate appropriate ingredients and arrange the atoms in order at the same time to grow epitaxy.

【Remark】The aforementioned contents have been appropriately simplified to be suitable for reading by the public, which might be slightly differentiated from the current industry situation. If you are the expert in this field and would like to give your opinions, please contact the writer. If you have any industrial and technical issues, please join the community for further discussion.